Q:
Every year our pond gets plagued with string and hair algae. We
check the pond several times a year and every time we check, the parameters of
the pond show that we have no nitrates, and everything is within its limits. Could
you please tell us why this nuisance algae keeps coming back year after year in
our pond?
A:
Cyanobacteria; these polyonymous bacteria are very misunderstood
Blue-green algae’s, known by many hobbyists as blanket weed, string and/or hair
algae (for all practical purposes the terms blanket weed, string algae,
Blue-green algae or hair algae are a metonymy meant for Cyanobacteria) will
eventually plague everybody’s pond at some time. It is often difficult to
overcome because the pond hobbyists failed to understand its cycle and the
exigency of the situation, so they wait far too long to intervene. Its long,
soft, and hair-like strands can swiftly cover an extensive area. Not only does
it become independent of bulk water nutrients once established, trap detritus
and/or debris can add further nutrients to the water column. This algae, is
bacteria, which many botanists classify as Blue-green algae, this particular
bacteria belonging to the kingdom Prokaryote which means “before the nucleus,”
and all other algae classified in the kingdom Protista.
The cells of Blue-green algae form strands and lack a distinct
nucleus, which contains no DNA inside. Instead, their DNA is simply floating
around freely in the cells, not contained in a discrete organelle. Bacterial
DNA is primary contained in chromosomes, just like ours, although structures called
plasmids contain bacterial DNA, as well. Unlike animals, bacterial cells also
have a cell wall, which differs from that of plants in the types of proteins
that make up the cell wall.
Cyanobacteria contain chlorophyll a,
which gives it a greenish color, but they also contain blue and/ or red lipid
soluble pigments (coloring matter). Many species can take nitrogen from the
air, convert it into compounds called nitrates, and therefore help fertilized
soil and water. Blue-green algae’s can use low light levels, contrary to what
most hobbyists believe. Most Blue-green algae reproduce only by cell division
and tiny spores packets called “sporangia” that form along its hair-like
strands. When these packages mature, they burst open and release spores that
settle and grow into “gametophytes,” which look like small green bubbles. When
these bubbles mature, they released male or female cells that eventually unite
and form a “zygote,” which is the base unit for the growth of a new structure
of hair algae.
Many hobbyists are accustomed to Blue-green algae forming a
slippery dark coating over rocks and boulders on their waterfalls.
Eutrophication of pond water has a large part in the growth rate of cyanobacteria.
Unlike our ponds that may become eutrophic in one or two seasons, lakes, and
ponds naturally become eutrophic over hundreds or thousands of years. The
actual cause of warping the ecology of a pond and accelerating it into
eutrophication are humans, this activity is called cultural eutrophication. Therefore, in a way, we have no one else to blame
but ourselves, when it comes to hair alga problems.
Our ponds support a natural
cycle of life processes. The bacteria of decay breakdown the waste of fish and
other organisms, releasing such nutrients as carbon dioxide, nitrate, and
phosphate. The hobbyists upset this natural balance when he or she adds too
many animals to the ponds bulk water and by overfeeding with foods that
contains phosphates. Many of the excess of nutrients that enters the bulk water
and causes problems come from the filtration system itself. Often, pond
hobbyists wonder why these growths persist when their nitrate and/or phosphates
levels appear to be very low to nonexistent. They exist because once
established the cyanobacteria growth need little or no nutrients from the bulk
water. They simply make their own nitrogen and phosphate needs in and below
their base structures with the hobbyists providing little else but a preferred environment
with which to live. In addition, initial growth is usually in an area that are
next to a small amount of nutrients found on or in rock crevices and gravel
bottoms, or on the sides of the pond walls where nutrients are abundant in bulk
water. Therefore, it is wiser to have nutrient users initially, than nutrient
sources and no means to dispose of them.
However, this is not as easy as it sounds. Cyanobacteria grows
best in nutrient rich systems, and where very low or no flow areas exists in
the pond. Spores are much like detritus (particulate organic carbon [POC],
organic and inorganic particles), and end up where the flow is the slowest. Cyanobacteria
are the only known group of organisms that are able to reduce nitrogen and
carbon in aerobic conditions. The water-oxidizing photosynthesis is
accomplished by coupling the activity of photosystems (protein complexes
involved in photosynthesis) PS-II and PS-I (Z-scheme; the light dependent reaction,
which converts solar energy into chemical energy). In anaerobic conditions,
they are also able to use only PS-I — cyclic photophosphorylation — with
electron donors other than water (hydrogen sulfide, thiosulfate, or even
molecular hydrogen) just like purple photosynthetic bacteria.
Cyanobacteria also have the ability to reduce elemental sulfur by
anaerobic respiration in the dark. A unique aspect of these organisms is that
their photosynthetic electron transport shares the same compartment as the
components of respiratory electron transport. It is the hyracoid membrane
(The site of the light-dependent reactions of photosynthesis.)
hosts both respiratory and photosynthetic electron transport, while the plasma
membrane contains only components of the respiratory chain.
It is also a fact that Cyanobacteria have developed the ability to
scavenge nitrogen from the atmospheric dinitrogen (N2) gas often dissolved in
water. This nitrogen is made from the Biocenosis clarification baskets in the
Anoxic filtration system from Dissimulative Denitrification. This is one reason
that the filtration system may become full of Cyanobacteria but the ponds main
body stays clear of such. Nitrogen is one of the building blocks of amino acids
and necessary to living organisms. However, even though nitrogen makes up 78%
of the atmosphere, it is locked away. This is also one way to tell if your
Anoxic filter is working properly and making N2 before the filter can eradicate
the cyanobacteria.
Cyanobacteria are able to break apart the molecule of dinitrogen
and capture the nitrogen gas by way of Nitrogenous enzymes. Nitrogenous enzyme
molecules are very large, complex enzymes, built of two twisted and balled-up
proteins, which combine and recombine to convert a molecule of N2 to two
molecules of usable ammonia (NH3). Though Nitrogenous enzymes enable conversion
of atmospheric nitrogen so that it can be employed in life processes, it is
ineffective in the presence of oxygen. To protect the Nitrogenous from oxygen,
many nitrogen-capturing Cyanobacteria (usually of the filamentous variety) have
developed special nitrogen-fixing cells called Heterocyst encased in thickened
cell walls. Because of this ability, low nitrate levels are generally not the
key to stopping this plague. Removing hydrogen sulfate producing obligatory
anaerobic bacteria in ponds is very important as well; this is more pragmatic
with rocks and stone at the bottom of ponds sitting on the pond liner surface.
There is also a correlation between setting up a pond this way and that of Blue
Green alga plagues.
The Anoxic Filtration System designed specifically to deal with
cyanobacteria especially in early spring and late fall when nutrients are at
their peak. Because the water is defused in the filtration system where the
flow rates are slower over a wider mass, will then act as a massive settlement chamber
for detritus and the spores of cyanobacteria. If the filtration system is set
up correctly these nutrients rich waters will never mix with the ponds main
bulk water. As hair algae and string algae begin to form in the filtration
system, the system will now begin to work overtime by (increasing the number
of bacteria related to nutrients) eradicate the nutrients that are now in the
system. These particular filtration systems will get loaded full of hair algae,
but the main pond stays algae free and crystal-clear. When the filtration
waters become nutrient poor, the cyanobacteria will then die off.
In the more commonly used filtration systems which water is being
forced through the filter medium, nutrient runoff, redistributes the waste and
further adds to nutrient accumulation mixing with bulk water and everything in
the pond becomes covered with hair and string algae. The nutrients are not
being contained in any one particular place; therefore, the entire pond becomes
a nutrient rich environment for cyanobacteria. For the hobbyists this means
doing whatever it takes to maintain phosphate below 0.015- ppm and nitrates
below 15-ppm. Since each pond is as different as Koi are, it is difficult to
say just what needs to be corrected and how. Many pond-hobbyists to eradicate
hair algae will want to use antibiotics, but this should be avoided. Most
antibiotics interfere with proteins in some way, including the structural and
transportation molecules in the cell wall, and enzymes, which are responsible
for the breakdown, synthesis, and transportation of substances through the
cell. The use of antibiotics such as
Tetracycline, Penicillin, or Erythromycin sulfate may eradicate
these unwanted algae (aka: Cyanobacteria) the first time, but further problem
blooms may persistently plague the pond, because of the bacteria mutating,
creating a bacterium into a superbug and therefore become less susceptible to
the antibiotics. You would be better off trying to get to the root of the problem
than to be administering antibiotics into the pond. In addition, remember that
antibiotics negatively affect biological filtration and can disrupt or even
wipeout the biological filter in our ponds, depending on the condition in the
filter and how much antibiotic were used.
Here are some helpful hints on trying to overcome Blue-Green alga
plagues:
1. Electrolytes and minor trace elements such as magnesium and
calcium are useful. This cannot be over emphasized enough to the hobbyist.
2. Adding an Ultraviolet Sterilizer (Very effective, not just for
sterilization, but for Redox which plays a role in controlling bacterial Blue
Green algae). The key for any UV unit to be effective is for proper
installation of such, with a well-designed unit, not a poorly designed unit
(often made by some manufacturers with cheap ineffective UV lamps). Make sure
your flow does not exceed 30-gph per watt (less is better) and that you have a
good flow pattern in your pond. This means trying to avoid any and all dead
spots in the pond. Sometimes adding air-stones and/ or more water movement by
pumps will do the trick. Do not think that a small 300-gph pump is going to
move enough water to make a difference in all but the smallest of aquatic environments,
it won’t. Buy yourself one or two of the Laguna Max-Flo 2900 pumps. These pumps
will move 2900-gph and only use about 130 watts of electricity. Increasing
circulation and dissolved oxygen is extremely important. These Prokaryote
Bacteria do not do as well in a well oxygenated and/or circulated environment.
3. Improving the Redox Potential, this is often missed; however
this is an important part of the equation.
4. Cutback on feedings and improve the quality of food you feed
your fish. This again will cut back on excessive nutrients. You want to aim for
less ammonia (not necessarily nitrates due to the properties of Cyanobacteria),
which is the result of poorly digested food.
5. Cutting back on the amount of sunlight that the pond receives a
day, although this is often recommended for the eradication of Cyanobacteria,
this is often not effective, and the Blue- Green alga will overcome such an
impediment. The reason is as stated above that Cyanobacteria have the ability
to reduce elemental sulfur by anaerobic respiration in the dark.
6. As with all ponds, limiting dissolved organic carbon can help,
but the bacteria-algae is capable of consuming all the carbon needed derived
from CO2. It is therefore important, to ensure a proper gas-off by water
movement and adjustments of water flow. The more oxygen created, the better the
degassing effect. Pond additives, such as alkalinity controllers, contain bicarbonates.
Bicarbonates convert into CO2, thus adding to the carbon levels. This also explains
why Cyanobacteria are a common problem in saltwater aquariums.
7. Pre-filtration such as a well maintained (frequently rinsed) pre-filter
can reduce organics and thus carbon. Skimmers are effective tools, but need to
be maintained frequently. Understanding the needs of cyanobacteria goes a long
way in the battle of unwanted Blue-green algae. It does not mean that the hobbyists
will necessarily win this particular battle once it has begun, but if the
hobbyists could prevent the battle to begin with then he or she has
accomplished a major victory in the
battlegrounds of their biotope.
Cyanobacteria
growing on the Biocenosis baskets inside the Anoxic filter.
However
it will not last long and if I had my druthers, which I do, I would choose my
cyanobacteria to be in my filter and not my pond.
No comments:
Post a Comment